Quasi crystalline inorganic oxide compositions prepared by neutral templating route

ABSTRACT

Crystalline inorganic oxide compositions having regular wormhole-like channels are described. The formation of the mesoporous composition is accomplished by hydrogen bonding between a neutral amine template in water and a water miscible organic solvent and a neutral inorganic oxide precursor, wherein there is an excess of an alkanol or water used to dissolve the template. The template can be removed and recycled.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of Ser. No. 09/192,172, filed Nov. 13,1998, continuation-in-part of which is pending U.S. application Ser. No.08/355,979, filed Dec. 14, 1994, U.S. Pat. No. 5,840,264 which in turnis a continuation-in-part of application 08/293,806 filed Aug. 22, 1994,now abandoned, and 08/527,504, filed Sep. 13, 1995 which is now U.S.Pat. No. 5,672,556.

U.S. GOVERNMENT RIGHTS

The invention described in this application was sponsored by theNational Science Foundation Contract CHE-9633798. The U.S. Governmenthas certain rights to this invention.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to new mesoporous quasi crystalline inorganicoxide compositions having regular worm hole shaped channels. Inparticular, the present invention relates to those compositions formedby a novel self-assembly method comprising steps of hydrogen bondingbetween a neutral amine template in water and a water miscible organicsolvent with a substantial excess of the water or the solvent, and aneutral inorganic oxide precursor, followed by hydrolysis andcrosslinking. This invention also relates to a route for facile recoveryand recycling of the template by simple solvent extraction.

(2) Description of Related Art

Porous solids created by nature or by synthetic design have found greatutility in all aspects of human activity. The pore structure of thesolids is usually formed in the stages of crystallization or subsequenttreatment. Depending on their predominant pore size, the solid materialsare classified as: (i) microporous, having pore sizes <20 Å; (ii)macroporous, with pore sizes exceeding 500 Å; and (iii) mesoporous, withintermediate pore sizes between 20 and 500 Å. The use of macroporoussolids as adsorbents and catalysts is relatively limited due to theirlow surface area and large non-uniform pores. Microporous and mesoporoussolids, however, are widely used in adsorption, separation technologyand catalysis. Owing to the need for higher accessible surface area andpore volume for efficient chemical processes, there is a growing demandfor new highly stable mesoporous materials. Porous materials can bestructurally amorphous, paracrystalline, or crystalline. Amorphousmaterials, such as silica gel or alumina gel, do not possess long rangeorder, whereas paracrystalline solids, such as γ- or η- A1₂O₃ arequasiordered as evidenced by the broad peaks on their X-ray diffractionpatterns. Both classes of materials exhibit a broad pore sizedistribution of pores predominantly in the mesoporous range. This widepore size distribution limits the shape selectivity and theeffectiveness of the adsorbents, ion-exchanges and catalysts preparedfrom amorphous and paracrystalline solids.

The only class of porous materials possessing rigorously uniform poresizes is that of zeolites and related molecular sieves. Zeolites aremicroporous highly crystalline aluminosilicates. Their lattice iscomposed by IO₄ tetrahedra (I=A1 and Si) linked by sharing the apicaloxygen atoms. Their pore network, which is confined by the spatiallyoriented IO₄ tetrahedra, consists of cavities and connecting windows ofuniform size (Breck D. W., Zeolite Molecular Sieves: Structure,Chemistry and Use; Wiley and Sons; London, 1974). Because of theiraluminosilicate composition and ability to discriminate small molecules,zeolites are considered as a subclass of molecular sieves. Non-zeoliticmolecular sieves are crystalline framework materials in which Si and/orA1 tetrahedral atoms of a zeolite lattice are entirely or in partsubstituted by other I atoms such as B, Ga, Ge, Ti, V, Fe, or P.

Zeolite frameworks are usually negatively charged due to the replacementof Si⁴⁺ by A1³⁺. In natural zeolites this charge is compensated byalkali or alkali earth cations such as Na⁺, K⁺ or Ca²⁺. In syntheticzeolites the charge can also be balanced by quaternary ammonium cationsor protons. Synthetic zeolites and molecular sieves are prepared usuallyunder hydrothermal conditions from aluminosilicate or phosphate gels.Their crystallization, according to the hereafter discussed prior art,is accomplished through prolonged reaction in an autoclave for 1-50 daysand, often times, in the presence of structure directing agents(templates). The proper selection of template is of extreme importancefor the preparation of a particular framework and pore network. A largevariety of organic molecules or assemblies of organic molecules with oneor more functional groups are known in the prior art to give more than85 different molecular sieve framework structures. (Meier et al., Atlasof Zeolite Structure Types, Butterworth, London, 1992). Excellent up todate reviews of the use of various organic templates and theircorresponding structures, as well as the mechanism of structuredirecting are given in Barrer et al., Zeolites, vol. 1, 130-140 (1981);Lok et al., Zeolites, vol. 3, 282-291 (1983); Davis et al., Chem.Mater., vol. 4, 756-768 (1992) and Gies et al. , Zeolites, vol. 12,42-49 (1992). For example, U.S. Pat. No. 3,702,886 teaches thatcrystallization of aluminosilicate gel (high Si/A1 ratio) in thepresence of quaternary tetrapropyl ammonium hydroxide template affordszeolite ZSM-5. Other publications teaching the use of various organicdirecting agents include, for example, U.S. Pat. No. 3,709,979, whereinquaternary cations, such as tetrabutyl ammonium or tetrabutylphosphonium, are used to crystallize zeolite ZSM-11 and U.S. Pat. No.4,391,785 demonstrating ZSM-12 preparation in the presence of tetraethylammonium cations. Another zeolite-ZSM-23 synthesis, directed by(CH₃)₃N⁺(CH₂)₇N⁺(CH₃)₃dications, is taught in U.S. Pat. No.4,619,820.The use of yet another dicationic template-N, N, N, N′, N′, N′,-hexamethyl-8,11-[4.3.3.0] dodecane diammonium diiodide, for thepreparation of zeolite SSZ-26, is shown in U.S. Pat. No. 4,910,006.

Other prior art teaches that primary amines such as propylamine, i -propylamine (U.S. Pat. No. 4,151,189), and diamines, such asdiaminopentane, diaminohexane and diaminododecane (U.S. Pat. No.4,108,881) also direct the synthesis of the ZSM-5 type structure.However, as pointed out by Hearmon et al., Zeolites, vol. 10, 608-611(1990), it is the protonated form of these amines which most likely isresponsible for the framework assembly.

In summary, most of the prior art zeolites and molecular sieveframeworks were assembled by using quaternary ammonium cations orprotonated forms of amines or diamines as templates.

The search for new organic directing agents, as evident in theincreasing number of prior art reports, is attributable to: (i) the needfor new and attractive types of stable frameworks and (ii) to the needfor expanding the uniform micropore size to mesopore region and thusallowing one to adsorb, process and discriminate among much largermolecules. However, the prior art molecular sieves typically possessuniform pore size in the microporous region. This pore size ispredetermined by the thermodynamically favored formation of frameworkwindows containing 8, 10 and 12 - I atom rings. Thus, the ability of theprior art zeolites and molecular sieves to adsorb, process anddiscriminate among molecules of certain shape and size is strictlylimited by the size of these windows. During the last three decadesconsiderable synthetic effort has been devoted to developing frameworkswith pore sizes larger than that of the naturally occurring zeolitefaujasite (pore size 7.4 Å). However, due to the above limitations, thesynthetic faujasite analogs, zeolite X or Y, with 8 Å pore windows(Breck D. W., Zeolite Molecular Sieves: Structure, Chemistry and Use;Wiley and Sons; London, 1974), maintained for decades their position asthe largest pore molecular sieves. The replacement of aluminosilicategels by alumino-and gallophosphate gels gave new direction to thesynthesis of large uniform pore materials. Thus, a 18-membered ringaluminophosphate molecular sieve VPI-5 (Davis et al. , Nature, vol. 331,698-699 (1988)), was found to possess a structure with an hexagonalarrangement of one-dimensional channels (pores) of diameter ≈12 Å. Thediscovery of a 20-membered ring gallophosphate molecularsieve-cloverite, exhibiting a uniform pore size of 13 Å is disclosed inEstermann M. et al., Nature, vol. 352, 320-323 (1991). Recently, Thomaset al., J. Chem. Soc., Chem. Commun., 875-876 (1992) reported a triethylammonium cation—directed synthesis of a novel 20-membered ringaluminophosphate molecular sieve, denoted JDF-20, having uniform poresize of 14.5 Å (calculated from lattice parameters). Very recently, apreparation of vanadium phosphate with 18.4 Å lattice cavity wasdisclosed in Soghmonian et al., Angew. Chem., Int. Ed. Engl., vol. 32,610-611 (1993). However, the actual pore size of these two materials isunknown since sorption data are lacking. In summary, in spite of thesignificant progress made toward the preparation of large pore sizematerials, all of the above mentioned molecular sieves still possessuniform pore size in the microporous region.

A breakthrough toward the preparation of mesoporous molecular sieveshave been disclosed recently in U. S. Pat. Nos. 5,098,684 and 5,102,643.The claimed class of mesoporous materials (denoted as M41S) of thisprior art was found to possess uniform and adjustable pore size in therange of 13-100 Å . In addition, these materials exhibited a smallframework wall thickness of from 8 to 12 Å and elementary particle sizeof usually much above 500 Å. Depending on preparation conditions M41Smaterials with hexagonal (MCM-41), cubic (MCM-48) or layeredcrystallographic structure have been disclosed (Beck et al., J. Am.Chem. Soc., vol. 114, 10834-10843 (1992). The postulated mechanism offormation of these materials involves strong electrostatic interactionsand ion pairing between quaternary ammonium liquid crystal cations, asstructure directing agents, and anionic silicate oligomer species (U.S.Pat. No. 5,098,684). Related mesoporous structures also have beenprepared by rearrangement of a layered silicate (kanemite) (Inagaki etal., J. Chem. Soc. Chem. Commun., vol. 8, 680-682 (1993)) in thepresence of quaternary ammonium cations. Recently, Stucky et al.(Nature, vol. 368, 317-321 (1994)) extended the electrostatic assemblyapproach by proposing four complementary synthesis pathways. Pathway 1involved the direct co-condensation of anionic inorganic species (I)with a cationic surfactant (S⁺) to give assembled ion pairs (S⁺I⁻), theoriginal synthesis of MCM-41 being the prime example (U.S. Pat. No.5,098,684). In the charge reversed situation (Pathway 2) an anionictemplate (S⁼) was used to direct the self-assembly of cationic inorganicspecies (I+) via S⁼I⁺ ion pairs. The pathway 2 has been found to give ahexagonal iron and lead oxide and different lamellar lead and aluminumoxide phases (Stucky et al., ibid). Pathways 3 and 4 involved counterion(X⁻ or M⁺ ) mediated assemblies of surfactants and inorganic species ofsimilar charge. These counterion-mediated pathways afforded assembledsolution species of type S⁺X^(−I+) (e. g., X⁻=Cl⁻, Br ) or, S⁻M⁺I⁻ (e.g., M⁺=Na⁺, K⁺), respectively. The viability of Pathway 3 wasdemonstrated by the synthesis of a hexagonal MCM-41 using a quaternaryammonium cation template and strongly acidic conditions (5-10 M HCl orHBr) in order to generate and assemble positively - charged frameworkprecursors (Stucky et al., ibid). In another example, a condensation ofanionic aluminate species was accomplished by alkali cation mediated(Na⁺, K⁺) ion pairing with an anionic template (C₁₂H₂₅OPO₃ ⁻). Thepreparation of the corresponding lamellar A1 (OH)₃ phase in this casehas been attributed to the fourth pathway (S⁻M⁺I⁻). Also, we havereported (Pinnavaia et al., Nature, vol. 368, 321-323 (1994)) thepreparation of a mesoporous silica molecular sieve and a Ti-substitutedanalogue by the acid catalyzed hydrolysis of inorganic alkoxideprecursors in the presence of primary ammonium ions produced by theacid.

Since all of the above pathways are based on charge matching betweenionic organic directing agents and ionic inorganic reagents, thetemplate is strongly bonded to the charged framework and difficult torecover. In the original Mobil approach (U.S. Pat. No. 5,098,684) thetemplate was not recovered, but simply burned off by calcination atelevated temperatures. Recently, it has been demonstrated that the ionicsurfactant in Pathway 1 materials could be removed by ion-exchange withacidic cation donor solution (U.S. Pat. No. 5,143,879). Also, thetemplate—halide ion pairs in the framework of acidic Pathway 3 materialswere displaced by ethanol extraction (Stucky et al., ibid). Thus, ionictemplate recovery is possible, provided that exchange ions or ion pairsare present in the extraction process.

While water molecules are easily removed by heating and evacuation, thequaternary ammonium cations, due to their high charge density, arestrongly bonded or confined to the pore cavities and channels of thenegatively charged framework. The same concepts are expected to applyfor the charge reversed situation were an anionic template is confinedin the pores of a positively-charged framework. Therefore, a cation oranion donor or ion pairs are necessary in order to remove the chargedtemplate from the framework of the prior art molecular sieves.

Textural porosity is the porosity that can be attributed to voids andchannels between elementary particles or aggregates of such particles(grains). Each of these elementary particles in the case of molecularsieves is composed of certain number of framework unit cells orframework-confined pores. The textural porosity is usually formed in thestages of crystal growth and segregation or subsequent thermal treatmentor by acid leaching. The size of the textural pores is determined by thesize, shape and the number of interfacial contacts of these particles oraggregates. Thus, the size of the textural pores is usually at least oneor two orders of magnitude larger than that of the framework-confinedpores. For example, the smaller the particle size, the larger the numberof particle contacts, the smaller the textural pore size and vice versa.One skilled in the art of transmission electron microscopy (TEM) candetermine the existence of framework-confined micropores from HighResolution TEM (HRTEM) images or that of framework-confined mesoporesfrom TEM images obtained by observing microtomed thin sections of thematerial as taught in U.S. Pat. No. 5,102,643.

One skilled in the art of adsorption could easily distinguish andevaluate framework-confined uniform micropores by their specificadsorption behavior. Such materials usually give a Langmuir type (TypeI) adsorption isotherm without a hysteresis loop (Sing et al., PureAppl. Chem., vol. 57, 603-619 (1985)). The existence of texturalmesoporosity can easily be determined by one skilled in the art of SEM,TEM and adsorption. The particle shape and size can readily beestablished by SEM and TEM and preliminary information concerningtextural porosity can also be derived. The most convenient way to detectand assess textural mesoporosity is to analyze the N₂ or Ar₂adsorption-desorption isotherm of the solid material. Thus, theexistence of textural mesoporosity is usually evidenced by the presenceof a Type IV adsorption-desorption isotherm exhibiting well definedhysteresis loop in the region of relative pressures Pi/Po>0.4 (Sing etal., Pure Appl. Chem., vol. 57, 603-619 (1985)). This type of adsorptionbehavior is quite common for a large variety of paracrystallinematerials and pillared layered solids.

The microporous zeolites and molecular sieves of the prior art exhibitmainly framework-confined uniform micropores, and no texturalmesoporosity as evidenced by their Langmuir type adsorption isothermswithout hysteresis loops at Pi/Po>0.4 and the large crystallineaggregate size of >2 μm, more usually from 5 to 20 μm. The typicalvalues for their specific surface area are from 300-800 m²/g and for thetotal pore volume ≲0.6 cm³/g (Perspectives in Molecular Sieve Science,Eds. Flank, W. H. and White T. E. Jr., ACS symposium series No. 368,Washington D. C., p. 247; 524; 544 (1988)). Most of these structures areprepared by prolonged crystallization at hydrothermal conditions, usingquaternary ammonium cations or protonated primary, secondary or tertiaryamines to assemble the anionic inorganic species into a framework. Itshould also be noted that the use in the prior art of neutral amines andalcohols as templates (Gunnawardane et al., Zeolites, vol. 8, 127-131(1988)) has led to the preparation of only microporous highlycrystalline (particle size >2μm) molecular sieves that lack appreciabletextural mesoporosity. For the mesoporous molecular sieves of the MCM-41family the uniform mesopores are also framework-confined. This has beenverified by TEM lattice images of MCM-41 shown in U.S. Pat. No.5,102,643. Therefore, the framework of this class of materials can beviewed as an expanded version of a hexagonal microporous framework. Theexistence of these framework-confined uniform mesopores was alsoconfirmed by the capillary condensation phenomenon observed in theiradsorption isotherms. A typical N₂ adsorption-desorption isotherm ofMCM-41 is shown in Davis et al., XIII North American Meeting of theCatalysis Soc., Book of Abstracts, p. D14 (1993). This adsorptionisotherm is essentially the same as that obtained previously by Sing etal., J. Chem. Soc., Chem. Commun., 1257-1258 (1993). The isotherm isconstituted by sharp adsorption uptake followed by a hysteresis loop inthe Pi/Po region of 0.3 to 0.4. This hysteresis corresponds to capillarycondensation into the framework-confined uniform mesopores. The lack ofappreciable hysteresis beyond Pi/Po >0.4 implies the absence of texturalmesoporosity. This lack of textural mesoporosity is also supported insome cases by the highly ordered hexagonal prismatic shaped aggregatesof size >2 μm (Beck et al., J. Am. Chem. Soc., vol. 114, 10834-10843(1992). The total pore volume of the material reported by Davis et al.is ≈0.7 cm³/g and that of the framework-confined mesopores, asdetermined from the upper inflection point of that hysteresis loop, isalmost equal to that of the total pore volume. Therefore, the ratio oftextural to framework-confined mesoporosity here approaches zero. Thesize of the framework-confined uniform mesopores is ≈30 Å.

In summary, the crystalline molecular sieve materials of theaforementioned prior art typically lack appreciable texturalmesoporosity. However, there is increasing number of reports in theliterature suggesting that textural mesopores behave as a transportpores to the framework-confined uniform pores and that they greatlyimprove the access and the performance of adsorbents, ion-exchangers andcatalysts. This, for example, is demonstrated in Pinnavaia et al.,Nature, vol. 368, 321-323 (1994); Chavin et al., J. Catal., vol. 111,94-105 (1988) and in Cartlidge et al., Zeolites, vol. 9, 346-349 (1989).According to this prior art, the transport pores provide more efficientassess to the framework-confined pores of the zeolite.

In summary, the prior art molecular sieve materials, as well as theirpreparation approaches have the following disadvantages:

1. The prior art uses charged surfactant ions (S⁺ or S⁻) as templates inorder to assemble an inorganic oxide framework from charged inorganicprecursors (I⁻ or I⁺). These charged templates are usually expensive,strongly bonded to the charged inorganic oxide framework and difficultto recover. In addition, some charged templates, such as quaternaryammonium ions are highly toxic and, therefore, potential health hazards.In all the prior art examples the electrostatically bonded templateswere removed from the framework by either a burning off process or by anion-exchange reaction with an ion donor solution. Also, ion pairs werenecessary in order to extract the template from the framework of pathway3 materials.

2. Yet other important disadvantages of the prior art mesoporousmolecular sieves are the small framework wall thickness (from 8 to 12Å), large elementary particle size (typically much above 500 Å) and theabsence of an optimal balance of framework-confined and texturalmesoporosity. This deficiency is attributable to the strongelectrostatic interactions and the specific preparation conditionsgoverning their self-assembly process. This does not contribute toimproving the thermal stability, the textural mesoporosity and toaccessing the framework-confined uniform mesopores. The lack of texturalmesoporosity could lead to serious diffusion limitations in manypotential applications. The ratio of textural to the framework-confinedmesoporosity of these materials is usually close to zero.

The aforementioned disadvantages of this prior art severely limit thepractical use of these crystalline materials.

Therefore, there is a need for new, templated, crystalline inorganicoxides with regular wormhole like channels. Also there is a need for anew method for the preparation of these mesostructures which would allowfor cost reduction by employing relatively expensive reagents and mildreaction conditions while at the same time providing for the effectiverecovery and recyclability of the template.

SUMMARY OF THE INVENTION

The present invention relates to a quasi crystalline inorganic oxidecomposition having framework-confined mesopores prepared by a methodwhich comprises reacting a neutral amine template and a neutralinorganic oxide precursor wherein the template is dissolved in asolution of water and a water miscible organic solvent containing alarger volume of either the alkanol or the water, aging of theprecipitate and removal of at least some of the template and the aqueoussolution to form the quasi crystalline composition which has regularwormhole shaped channels.

Further, the present invention relates to a method for the preparationof a synthetic, quasi crystalline inorganic oxide composition whichcomprises: (a) preparing a first solution of a neutral inorganic oxideprecursor; (b) preparing a second solution of a neutral amine templatein water and a water miscible organic solvent by stirring it at atemperature between about minus 200° and plus 1000° C., wherein thesolutions together contain a volume excess of the water or the alkanol;(c) mixing of the solutions of steps (a) and (b) at a temperaturebetween about minus 20° and plus 100° C. to form a precipitate which isaged to form the quasi crystalline inorganic oxide composition; (d)separating at least some of the template from the crystallinecomposition; and (e) optionally calcining the quasi crystallinecomposition.

OBJECTS

An object of the present invention is to provide novel quasicrystalline, inorganic oxide compositions with regular wormhole shapedchannels.

Another object of the present invention is to provide inexpensivepreparation methods for these materials which avoid the use of chargedionic templates and charged inorganic oxide precursors and hightemperature hydrothermal synthesis conditions.

Still another object of this invention is to provide for the facilerecovery and recycling of the template by new separation art involvingsimple solvent extraction from the quasi crystalline inorganic oxidecomposition.

These and other objects will become increasingly apparent from thefollowing description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing N₂ adsorption-desorption isotherms for thesilicas assembled at ambient temperatures from dodecylamine andtetraethyl orthosilicate (TEOS) : Curves A and B are for derivativesobtained from a water-rich solution (water:ethanol=90:10 (v/v)) andethanol-rich solution (water:ethanol=35:65 (v/v)) and curves C and D arefor derivatives prepared from the same water-rich and ethanol-richsolutions, but in the presence of mesitylene (Mes/S°=of 1.0). The HKvalues are the Horvath-Kawazoe pore diameters.

FIG. 2 is a graph showing N₂ adsorption-desorption isotherms for thesilicas prepared from tetradecylamine and TEOS in water-rich andethanol-rich solution. The labeling of the isotherms A to D is the sameas in FIG. 1.

FIGS. 3A and 3B are graphs of N₂ adsorption-desorption isotherms for asilica prepared from dodecylamine in water-rich solution in the presenceof mesitylene (Mes/S=4.5): (A) after calcination at 650° C. withretention of framework and textural mesopores and (B) after calcinationat 1000° C. with collapse of framework pores but with retention oftextural pores. FIG. 3C: Horvath-Kawazoe pore size distribution aftercalcination at 650° C.

FIGS. 4A to 4D are photographs of TEM images of calcined (650° C.)molecular sieve silicas assembled from dodecylamine and TEOS. FIG. 4Ashows mesoscale fundamental particles and fractal-like texture obtainedfrom water-rich solution; FIG. 4B shows the spheroid fundamentalparticles and macroscale beads-on-a-string texture obtained fromethanol-rich solution. FIGS. 4C and 4D show the wormhole-like frameworkpores obtained from water-rich solution.

FIGS. 5A and 5B are photographs showing TEM images of the silicamolecular sieves prepared from dodecylamine and TEOS in water-richsolution in the presence of mesitylene (Mes/S=4.5) and calcined at 1000°C. to collapse the framework pore structure; FIG. 5A is a lowmagnification image showing the retention of the textural mesopores andFIG. 5B is a high magnification image showing the absence of frameworkpores.

FIG. 6 is a photograph of an x-ray powder diffraction pattern ofcalcined (650° C.) silica molecular sieves assembled from dodecylamineamine and TEOS in water-rich and ethanol-rich solution with or withoutmesitylene as an auxiliary structure director.

FIG. 7 is a schematic representation of the structure-directing effectsof mesitylene on silica molecular sieve assembly. In the water-richmedia, the mesitylene “dissolves” in the hydrophobic central core of themicelle leading to pore expansion. In the ethanol-rich environment,mesitylene preferentially “adsorbs” to interfacial head groups, thusincreasing effective head group size and subsequently decreasing thepore size.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to a quasi crystalline inorganic oxidecomposition with regular wormhole shaped channels. The templatingmechanism comprises reacting a neutral amine template solutioncontaining water a miscible organic solvent, preferably an alkanolcontaining 1 to 10 carbon atoms, with an excess of one or the other anda neutral inorganic oxide precursor solution to form a reaction product,hydrolysis of the reaction product, and the subsequent removal of theaqueous solution and the template.

The framework-confined uniform pores are pores formed by nucleation andassembly of the framework elementary particles. These pores typicallyare cavities and channels confined by the solid framework.

The size of the cavities and channels, i.e. the size of theframework-confined uniform pores, in molecular sieve materials ispredetermined by the thermodynamically favored assembly routes. Theframework-confined pores of freshly crystallized product are usuallyoccupied by the template, water and alkanol molecules.

The quasi crystalline inorganic oxide compositions of the presentinvention are obtained by a new neutral preparative method. Theformation of the mesoporous structures is accomplished primarily byH-bonding between a neutral template and a neutral inorganic oxideprecursors, followed by further hydrolysis and crosslinking of IO_(m)units, where I is a central metallic or non-metallic element coordinatedto m oxygen atoms (2<m<8). Specifically, the said method comprises theformation of a precipitate by mixing of a neutral template solution witha neutral inorganic oxide precursor, preferably a inorganic alkoxide ora neutral inorganic oxide sol, in the presence of a molar excess amountover the inorganic oxide of water and alkanol, preferably ethanol ormethanol. Much of the template can be recovered by extraction of thetemplated product with water or with ethanol, or a mixture thereof, orby vacuum distillation. Preferably, the template is removed byextraction with ethanol. Complete removal of the last traces of templateand the further crosslinking of the IO_(m) framework is accomplished bycalcination at 300° to 1000° C.

Hydrogen bonding between the template and the reagent is the primarydriving force of the framework assembly process of this invention. Theneutral amine plays the role of both a solvent and template for theneutral precursor. Water plays a role of hydrolyzing reagent and thealcohol acts as co - solvent.

The template solution is preferably augmented with an additionalstructure directing agent. This is an organic compound which isessentially insoluble in water, but soluble in the miscible organicsolvent. The preferred compounds are non-polar.

The molar ratio of amine to inorganic oxide precursor in the initialreaction mixture is between about 0.05 and 3, preferably about 0.05 andabout 1.4. The crystalline inorganic oxide composition of the presentinvention preferably has in its as - synthesized and anhydrous state thefollowing formula:

A_(X)Si_(y)O_(z)

wherein A is selected from the group consisting of Ca, Mg, Zn, Cu, B,Al, Ga, Cr, Fe, Ge, Ti, V, Zr, V, Sn, W and Mo, x is between 0 to 1.0, yis between about 0 and 1.0 and z is between about 1.0 and 3.0 and thesum of x +y is equal to 1.0.

The quasi crystalline mesoporous materials of this invention may becharacterized as formed by H-bonding between neutral inorganic oxideprecursors containing I-OH groups as hydrogen donors and a neutral aminetemplates as hydrogen acceptors, followed by further hydrolysis andcrosslinking of IO_(m) units under mild reaction conditions.Specifically, the method comprises formation of a precipitate by mixingof a neutral amine template solution with a solution of at least oneinorganic oxide precursor, preferably an inorganic alkoxide, or aneutral inorganic oxide sol or gel precursor in the presence of a waterand alkanol with an excess of either the water or the alkanol, followedby hydrolysis and aging under stirring at temperature of at least minus20° C. for at least 0.5 h.

The compositions can be used as an adsorbents, ion-exchangers or acatalysts. According to this invention, the removal of the template fromthe reaction product can be achieved by at least four ways: (i) airdrying followed by calcination in air or in inert gas at temperaturefrom 300-1000° C. for 30 min to 72 h; (ii) solvent extraction of thetemplated product; and (iii) by vacuum distillation of the product; (iv)by various combinations of (i) to (iii). The fact that the template canbe recycled by non-ionic recovery methods (ii) and (iii) is also adistinctive feature of this invention. Procedure (i) results in thedestruction of the template. The separation of the template byextraction or distillation should be followed by air drying andcalcination in air or inert gas to remove the final traces of templateand to complete the crosslinking of the mesostructure.

After template removal and calcination, the said material can be used asan adsorbent for non-polar or polar organic molecules or as a gas dryingagent. Furthermore, the said calcined product when frameworksubstituted, or subsequently impregnated, as taught in Sachtler, W. M.H., Catal. Today 15, 419-429 (1992), with proper amount of catalyticallyactive element, such as Al, Ti, V, Pt, Pd, Cu, Cr or mixture thereof, orwhen functionalized with metal salts or organometallic compounds couldbe used as a catalyst for cracking, hydrocracking,hydrogenation-dehydrogenation, isomerization, polymerization or redoxreactions involving organic substrates.

The new preparation method of the composition of this invention involvesthe preparation of solutions comprising sources of di-, tri-, tetra-,penta- or hexavalent elements, or mixture thereof, a solvent (optional),aging and reacting this solution with template solution at mild reactionconditions, under stirring, until formation of the desired crystallineproduct and recovering the crystalline material. The template, can bedescribed more particularly as a neutral (non-ionic) molecule of formulaR₁R₂R₃N, wherein N is nitrogen and at least one of R₁, R₂ and R₃ isselected from the group of alkyl of from 6 to 22 carbon atoms or aryl offrom 6 to 18 carbon atoms or combination thereof. The remaining R groupsare selected from the group consisting of hydrogen or alkyl from 1 to 22carbon atoms or combination thereof.

The preparation procedures of the compositions comprise steps asfollows:

(i) preparing a solution of neutral inorganic oxide precursor,preferably an inorganic alkoxide of a di-, tri-, tetra-, penta- orhexavalent element or mixture thereof in the presence (optional) ofhydrolyzing agent and/or co-solvent in a molar excess of one or theother;

(ii) preparing a solution of the neutral template in a water and ethanolwith a molar excess of the alkanol or the water;

(iii) reacting the inorganic oxide precursor solution with the templatesolution by stirring at a temperature from minus 20° C. to plus 100° C.to produce a precipitate;

(iv) air drying the precipitate and/or separating the template by eitherextraction with water or alcohol or a mixture thereof, or bydistillation of the templated product. After template removal, thecomposition is subjected to calcination to remove trace amounts oftemplate and to complete the crosslinking of the framework; and

(v) Calcining the product at 300 to 1000° C. in air or inert gas for atleast 30 min.

The inorganic oxide solutions are prepared from neutral precursors suchas the silicates of Ser. No. 08/293,806, filed Aug. 22, 1994 and such asalkoxides, inorganic hydrocarbons such as silanes, or inorganiccomplexes which upon hydrolysis afford a I-OH species. The list ofpreferred alkoxides include, in particular, aluminum(III) tri-ethoxide,aluminum(III) isopropoxide, aluminum(III) n-, tert - or sec- butoxide,antimony(III) isopropoxide, antimony(III) n-butoxide, calcium(II)ethoxide, calcium(II) isopropoxide, calcium(II) tert- butoxide,chromium(IV) tert-butoxide, chromium(III) isopropoxide, copper(II)methoxyethoxide, gallium(III) isopropoxide, germanium(IV) ethoxide,germanium(IV) isopropoxide, indium(III) isopropoxide, iron(III)ethoxide, iron(III) tert - butoxide, iron(III) isopropoxide, lead(II)isopropoxide, lead(II) tert - butoxide, magnesium(II) ethoxide,molybdenum (V) isopropoxide, manganese (II) isopropoxide, niobium(V)ethoxide, strontium(II) isopropoxide, tetramethyl orthosilicate,tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate, tetrabutylorthosilicate, tetrahexyl orthosilicate, H[OSi(OC₂H₅)₂]OH where n=4−6,RSi(OR)₃, tin(IV) isopropoxide, tetraethyl orthotitanate, tetrapropylorthotitanate, tetraisopropyl orthotitanate (TIPOT), tetrabutylorthotitanate, tetraoctadecyl orthotitanate, tungsten(VI) ethoxide,tungsten(VI) isopropoxide, vanadium(V) triisopropoxide oxide, zinc(II)isopropoxide, zinc(II) tert- butoxide, zirconium(IV) n-propoxide,zirconium(IV) isopropoxide, zirconium(IV) tert- butoxide or mixturesthereof. Also, a variety of a neutral colloidal inorganic oxideprecursor solutions or inorganic oxide gels also can be used to preparethe compositions of the present invention. For example, a potentialsource of a neutral silica include the variety of commercially availablefumed silicas or silica gels.

The co-solvent is selected from the group of normal or isomerizedalcohols having 1 to 12 carbon atoms and at least one OH group, such asmethanol, ethanol, propanol, butanol, hexanol, octanol, dodecanol. Morepreferably, said co-solvent is methanol, ethanol, propanol, 2 -propanolor mixture thereof. Those skilled in the art will know that polyols inwhich more than one OH group is present also can be used as aco-solvent.

The reacting of the inorganic oxide precursor solution and templatesolution is preferably carried out at 20 to 75° C. by random order ofreagent addition, preferably by adding the inorganic oxide precursorsolution to the stirred template solution. More specifically, saidreacting is performed by H-bonding between neutral inorganic oxideprecursors and a neutral template, followed by further hydrolysis andcrosslinking of IO_(m) units at mild reaction conditions. This H-bondingmost likely occurs generally between any I-OH or I-proton donor compoundand the lone pair of electrons on the central atom of the head group ofthe organic template.

The calcinating is performed by heating in an oven at a temperaturepreferably from 300-650° C. for 4 h.

The outstanding features of the present method are:

(i) The use of neutral templates, particularly amines or diamines, in analkanol, preferably methanol or ethanol, and water with a volume excessof one or the other to assemble the mesoporous framework structure;

The templated inorganic oxide compositions of the present invention canbe combined with other zeolites or clays or inorganic oxides or organicpolymers or mixture thereof, in order to prepare adsorbents,ion-exchangers, catalysts, catalytic carriers or composite membraneswith high thermal and mechanical resistance. In addition, one skilled inthe art can impregnate the composition of the present invention or useit as an encapsulating agent for transition metal macrocycles such asphthalocyanines and porphyrins. The active phase in these cases could bea transition metal for example Cu, Co, Ni, Fe, Ti, V, W, Pt, Pd or Mo ormixtures thereof. These catalysts can be used in conversion such ascatalytic cracking, hydrocracking, reforming, isomerization,dealkylation or oxidation in the presence or absence of H₂O₂ or O₂ ormixture thereof.

The following specific examples are intended to be illustrative of thepresent invention, but are not intended to limit the invention.Water:ethanol solvent mixtures of differing polarity have been used totailor the framework and textural mesopores of silica molecular sievesthrough an electrically neutral (S°I°) assembly pathway (S°=dodecyl ortetradecylamine; I°=tetraethyl orthosilicate). Mesostructure assemblyfrom a water-rich solvent mixture, water:ethanol =90:10 (v/v), affordedwormhole-like channels with a complementary textural pore volume equalin magnitude to the framework pore volume. An ethanol-rich mixture,water:ethanol =35:65 (v/v) also formed wormhole-like channels, but thetextural porosity was less than 20% of the framework pore volume.Mesostructured derivatives with high textural porosity were comprised ofmesoscale fundamental particles with a fractal-like surface andaggregate into larger particles with low mass fractal dimensions. Incontrast, mesostructures with low textural porosity were assembled intomuch larger aggregates of macroscale spheroid to disk-shaped fundamentalparticles. The differences in particle textures were attributed todifferences in I° hydrolysis rates and S°I° nucleation and growth ratesin the two solvent systems. The presence of mesitylene and otherhydrophobic organic molecules in the reaction mixtures resulted in anexpansion of the framework pores under water-rich conditions. Porecontraction, however, was observed with mesitylene present underethanol-rich conditions. This versatile structure-modifying property ofmesitylene in S°I° assembly is explained by the solvent-dependentbinding of the aromatic molecules to two structurally distinct andsize-altering “dissolved”and “adsorbed” states at the centers andinterfacial surfaces of the surfactant micelle, respectively. Thus, boththe framework and textural pores of the silica can be readily tailoredto the needs of a particular materials application through S°I° assemblyby a judicious choice of an appropriate solvent and an auxiliarystructure modifier.

Although they are distinguishable with regard to structural ordering,MCM-41 and the molecular sieves of the present invention both exhibit asharp step in their nitrogen adsorption isotherms, corresponding to thepresence of a regular mesoporous framework. Owing to the very smallelementary particle size of many mesostructured derivatives, they canexhibit complementary textural mesopores, in addition to frameworkpores. The textural pore volumes can be up to 1.5 or more times as largeas the framework pore volumes, whereas MCM-41 exhibits very littletextural mesoporosity (Schmidt, R. E., et al., J. Am Chem. Soc. 117;4049 (1995)). The textural mesopores are important because they greatlyfacilitate mass transport to the framework mesopores.

Another potential benefit of S°I° assembly is the possibility ofconducting mesostructure synthesis in media of diverse polarity. Unliketheir ionic counterparts, S° and I° reagents are generally soluble in awide range of solvents. Thus, salvation effects on the rates ofhydrolysis and assembly might be an effective means of controllingstructure. One of the objectives of the present invention is to showtailoring of both the framework and the textural mesopores of themesostructured molecular sieves by controlling the polarity of thereaction medium in which the assembly process is carried out. Thepresent invention makes use of water:alkanol compositions to controlsolvent polarity, textural porosity and framework porosity.

The role of mesitylene as an auxiliary structure-directing agent wasinvestigated in both water-rich and alkanol-rich solvent systems. Byusing salvation effects to shift the equilibrium between structurallydistinct binding states of mesitylene in the surfactant micelles(Mukerjee, P., et al., J. Phys. Chem. 82:1620 (1978); and Gordon, J. E.,et al., J. Phys. Chem. 74:957 (1970)), we are able to effect anexpansion or contraction of the framework pore structure mesoporosity.The ability to control both framework and textural mesoporosity can beof great value in designing mesostructured materials as catalysts,adsorbents and sensor materials.

EXAMPLES 1 to 4

Silica molecular sieves were prepared by S°I° assembly pathways inwater:ethanol solvent mixtures of differing composition and polarity. Inboth reaction media tetraethyl orthosilicate (TEOS) served as theneutral silica precursor and dodecylamine and tetradecylamine were theneutral structure director. In a typical synthesis the surfactant wasdissolved in ethanol, and then the desired amount of water was addedunder vigorous stirring to obtain a homogeneous solution. TEOS was addedto the surfactant solution and the mixture was allowed to react understirring at ambient temperature for about 20 hours. The reactions werecarried out in an open beaker in a well ventilated hood to allow forsome evaporation of solvent and concentration of the solid reactionproducts. When mesitylene was used as an auxiliary structure director,it was added to the surfactant solution and stirred for 15 minutesbefore the addition of TEOS. All of the reaction products were filtered,dried in air, and calcined at 650° C. in air for 4 hours.

For the purposes of probing the effect of solvent polarity on texturalporosity, it was desirable to form silica molecular sieves fromwater-rich and ethanol-rich solutions with equivalent frameworkporosities. To achieve the framework pore structures, we used reagentconcentrations in the ethanol-rich system that were twice theconcentrations for the water-rich medium. For the silica molecularsieves assembly in the relatively low polarity, ethanol-rich reactionmedium, where water:ethanol volume ratio was 35:65, the molarcomposition of the reaction mixture was 1.0 TEOS:0.25 Surfactant : 18EtOH : 34H₂O. For assembly in a relatively high polarity, water-richsolvent mixture, namely, 90:10 (v/v) water:ethanol, the molarcomposition was 1.0 TEOS : 0.25 Surfactant : 10 EtOH:130 H₂O.

Powder X-ray diffraction patterns were measured using Cu-Kα radiation(λX=1.542 Å and a Rigaku Rotaflex diffractometer equipped with arotating anode operated at 45 kV and 100 mA. The scattering andreceiving slits were ⅙ degree and 0.3 degree, respectively.

N₂ adsorption and desorption isotherms at −196° C. were obtained on aCoulter Omnisorp 360CX Sorptometer operated under continuous adsorptionmode. Pore size distributions were calculated from the N₂ adsorptionbranch using the Horvath-Kawazoe model (Horvath, G., et al., J. Chem.Eng. Jpn. 16:470 (1983)).

Transmission electron microscopy (TEM) studies were carried out on aJEOL 100CX instrument using an electron beam generated by a CeB₆filament and an acceleration voltage of 120 kv. The resolution of theinstrument was about 6 Å, as estimated by indirect measurement of thespherical aberration constant (Spence, J. C. H., “ExperimentalHigh-Resolution Electron Microscopy”, P264, Oxford University Press, NewYork (1988)) under medium-high magnification (i.e., 100,000X).Therefore, it was possible to resolve pores above about 30 Å. Thespecimens were prepared by dipping a carbon coated copper grid into asuspension (0.1 wt%) of mesoporous material in ethanol that waspre-sonicated for 10 minutes. Attempts to use thin-sectioned specimenswere abandoned, because thin sectioning caused damage and loss oftexture pore information.

Two versions of silica molecular sieves were prepared through S°I°assembly at ambient temperature in reaction media that differed insolvent polarity. In one reaction system the mesostructures were formedfrom a “water-rich” solution of 90:10 (v/v) water:ethanol. The otherreaction medium was a less polar “ethanol-rich” solution of 35:65 (v/v)water:ethanol. Two S°surfactants, namely, dodecylamine andtetradecylamine, were used as structure directors. The reactionstoichiometries were the same for both the water-rich and theethanol-rich reaction systems (S°/I°=0.25). When mesitylene (Mes) waspresent as an auxiliary structure director, the Mes/S° molar ratio was1.0 or 4.5.

FIGS. 1 and 2 provide N₂ adsorption-desorption isotherms for the silicamolecular sieves obtained from dodecylamine and tetradecylamine asstructure directors, respectively. The adsorption properties of themesostructures assembled from the two surfactants under the samereaction conditions are qualitatively equivalent. As can be seen fromthe isotherms labeled A and B in both Figures, the structures obtainedfrom the water-rich and ethanol-rich solutions give stepped-shapedisotherms at P/Po <0.4. The positions of the steps correspond toHorvath-Kawazoe pore sizes of 28-29 Å(S°=C₁₂H₂₅NH₂) and 33-35Å(S°=C₁₄H₂₉NH₂).

Although the mesostructures obtained from the water-rich andethanol-rich media have equivalent frameworks, the texturalmesoporosity, as evidenced by the N₂ adsorption/desorption in thepartial pressure region P/Po >0.4, depends dramatically on the polarityof the medium used for assembly. A textural pore volume even larger thanthe framework pore volume can be obtained from the water-rich system,whereas the ethanol-rich medium generates a mesostructure with little orno textural pores. As will be seen from TEM images presented below, thehigh textural mesoporosity for the water-rich system is associated withthe presence of extremely small fundamental particles.

We consider next the effect of mesitylene on the framework porestructure and textural mesoporosity of the silica molecular sievesassembled from water-rich and ethanol-rich solutions. The structuremediating properties of mesitylene is manifested in theadsorption-desorption curves labeled C and D in FIGS. 1 and 2. Thepresence of mesitylene at Mes/S°=1 in the water-rich systems causes theadsorption step to be significantly shifted to higher relative pressure.The shift in the step position corresponds to a 3-5 Åincrease in HK poresize. In the ethanol-rich medium, however, the presence of mesityleneresults in a shift of the step position to lower relative pressures,corresponding to a 5-7 Å decrease in HK pore diameter.

Although mesitylene can substantially expand or contract the frameworkpores depending on the polarity of the reaction medium, it does notalter the key role of the solvent in regulating the textural porosity.As will be shown below, mesitylene actually increases the texturalmesoporosity under water-rich assembly conditions, but it has only aminor influence on the extremely low textural pore volume of the productwhen assembled under ethanol-rich conditions.

EXAMPLE 5

To further probe the influence of mesitylene on the framework poresassembled from a water-rich environment, we repeated the assemblyprocess in 90:10 (v/v) water:ethanol at a much higher Mes/S° ratio of4.5. As shown by the N₂ isotherms in FIG. 3, the adsorption step due toframework pore filling is further shifted to higher relative pressure asa consequence of a HK pore size (38 Å) that is 9 Å larger than the valueobtained in the absence of mesitylene. The insert to FIG. 3 shows thehalf width of the HK pore distribution to be ˜10 Å, a value typical ofmesoporous molecular sieve materials. On the basis of the hysteresisloop at higher relative pressure, it appears that the textural porevolume is substantially increased by ˜50% from ˜550 ml STP/g in theabsence of mesitylene to ˜850 ml STP/g by the presence of mesitylene.

EXAMPLE 6

In order to verify that the textural pores do indeed arise frominterparticle voids and not from a large pore component of theframework, the silica molecular sieve assembled from S°=C₁₂H₂₅NH₂ at90:10 (v/v) H₂O:ethanol and Mes/S°=4.5 was calcined at 1000° C. tocollapse the framework pores. The N₂ adsorption/desorption isotherms aregiven by curve B of FIG. 3. Note that the framework pores indeed havecollapsed, as signified by the loss of the pore filling step, but asubstantial fraction (>50%) of the textural porosity is retained. Thus,the textural porosity cannot be a consequence of framework structure.

EXAMPLES 7 and 8

The TEM images shown in FIGS. 4A and 4B provide insights into theframework structure and textural mesoporosity associated with silicamolecular sieves assembled from water- and ethanol-rich media. Regularframework pores are readily observed, regardless of solvent system usedto prepare the products. It is quite clear that the pores originate fromthe space initially occupied by uniform supramolecular assemblies ofsurfactant, but there is no apparent long range order to the porearrangement. Instead the pore packing motif is more wormhole-like,perhaps, even sponge-like, in character.

The most important distinguishing feature between the water- andethanol-rich reaction products is the particle texture. As shown in FIG.4A, the water-rich reaction mixture yields mesoscale fundamentalparticles. These fundamental particles aggregate into larger particleswith interparticle voids on a mesoscale. These textural mesopores arecomparable in size to the mesoscale fundamental particles. In contrast,the ethanol-rich medium forms spheroid to disk-like fundamentalparticles that are typically 100 nm or larger in size (see FIG. 4B) .These macroscale fundamental particles are linked into larger aggregateswith a beads-on-a string texture. The interparticle voids are muchlarger, typically in the macropore range (>50 nm). FIGS. 4C and 4Dprovide higher resolution images of the wormhole to sponge-likeframework structure obtained from water-rich solution.

EXAMPLE 9

FIGS. 5A and 5B provide TEM images for a silica molecular sieveassembled from water-rich solution in the presence of a relatively highconcentration of mesitylene (Mes/S°=4.5) but calcined at 1000° C. tocollapse the framework mesopore structure. FIG. 5A, obtained at lowmagnification, shows the retention of the textural pores. FIG. 5B,obtained at higher magnification, shows that the framework mesoporesindeed have been destroyed by thermal treatment. This result, which isconsistent with the N₂ adsorption results described earlier (cf., FIG.3), further identifies the interparticle voids as being the origin ofthe textural mesopores.

EXAMPLES 10, 11, 12, 13 and 14

FIG. 6 provides the X-ray powder diffraction patterns for silicamolecular sieves assembled from C₁₂H₂₅NH₂ as the structure director.Structures formed from C₁₄H₂₉NH₂ showed qualitatively equivalentdiffraction features. The patterns all contain a strong, relativelybroad reflection at 2.0-3.0°2θ and a very weak broad shoulder in theregion near 5.0°2θ. The qualitative form of the patterns is not affectedby the water- or ethanol-rich polarity of the assembly medium or by thepresence of mesitylene. However, the positions of the intense reflectionand the weak broad shoulder are dependent by the polarity of thereaction medium and by the presence of mesitylene.

Table 1 summarizes the basal spacings, HK pore sizes, N₂ BET surfaceareas (SBET), total liquid pore volumes (V_(t)), liquid framework porevolumes (V_(fr)), the ratio of textural to framework pore volumes(V_(tx)/V_(fr)), and the bulk densities for the silica molecular sieves.

TABLE 1 Physical parameters for calcined (650° C.) molecular sievesilicas prepared by S^(o)I^(o) assembly in H₂O-rich and EtOH-rich mediumH-K d pore S_(BET) V_(t) V_(fr) d_(bulk) S^(o) Reaction Medium^(a) (Å)(Å) m²/g cc/g cc/g V_(tx)/V_(fr) g/cc C₁₂H₂₅NH₂ H₂O-rich; MES/S^(o) = 041.7 29 1035 1.30 0.62 1.10 0.33 H₂O-rich; MES/S^(o) = 1.0 43.3 32  9931.37 0.65 1.11 0.21 H₂O-rich; MES/S^(o) = 4.5 48.0 38  957 1.63 0.631.59 0.16 EtOH-rich; MES/S^(o) = 0 39.4 28 1070 0.66 0.56 0.18 0.53EtOH-rich; MES/S^(o) = 1.0 34.0 21 1464 0.51 0.48 0.06 0.67 C₁₄H₂₉NH₂H₂O-rich; MES/S^(o) = 0 44.2 34 1035 1.28 0.65 0.97 0.35 H₂O-rich;MES/S^(o) = 1.0 50.2 40  927 1.30 0.67 0.94 0.20 H₂O-rich; MES/S^(o) =4.5 55.2 45  900 1.67 0.67 1.49 0.16 EtOH-rich; MES/S^(o) = 0 49.1 33 936 0.69 0.61 0.13 0.57 EtOH-rich, MES/S^(o) = 1.0 38.7 28 1117 0.620.57 0.09 0.65 ^(a)The compositions of H₂O-rich and EtOH-rich solutionswere 90:10 and 35:65 (v/v) for H₂O:EtOH, respectively

The basal spacings represented by the strong diffraction line arecorrelated with the HK pore sizes, even though the framework lacksregular long-range order. The BET surface areas are in the range700-1500 m²/g. The incorporation of mesitylene into the synthesis ofsilica molecular sieves from a water-rich medium increases the HK poresize and decreases the surface area of the mesostructure. Conversely,mesitylene decreases the pore sizes and increases the surface areas ofsilica molecular sieves assembled from ethanol-rich solution.

It is especially noteworthy from the results in Table 1 that the totalpore volumes are much larger for the products derived from a water-richmedium (˜1.3-1.7 cc/g) than an ethanol-rich medium (˜0.5-0.7 cc/g). Yet,the framework pore volumes are confined to the approximate range 0.5-0.7cc/g. The difference between the total and framework pore volumes isexpressed as the textural pore volume, V_(tX). For products assembledfrom a water-rich medium, the textural pore volume can be up to 1.6times as large as the framework volume depending on the amount ofmesitylene used as a structure modifier. In contrast, the textural porevolume for products obtained from an ethanol-rich medium is equivalentto only a small fraction (6-18%) of the framework volume. Finally, thedifferences in total pore volumes is manifested in the bulk densities,which are substantially lower for products derived from a water-richmedium (0.16-0.35 g/cc) than an ethanol-rich medium (0.53-0.67 g/cc).

The results of the present invention demonstrate several importantadvantages of S°I° assembly for the preparation of mesoporous metaloxide molecular sieves. In the case of silica molecular sieves, we haveshown through N₂ adsorption studies that the textural mesoporosity,which greatly facilitates access to the framework mesopores, can becontrolled by a judicious choice of solvent (cf., FIGS. 1 and 2). Awater-rich solvent, such as 90:10 (v/v) water:ethanol, promotes theformation of mesopore fundamental particle sizes. TEM images show thatthe interparticle voids responsible from the textural mesoporosity areon length scale comparable to the fundamental particles (cf., FIG. 4A).Conversely, a solvent of lower polarity, namely, 35:65(v/v)water:ethanol, minimizes the textural porosity by forming much largerfundamental particles (cf., FIG. 4B). There is no doubt that thetextural mesoporosity for the product assembled from 90:10 (v/v)water:ethanol arises from interparticle pores. Hysteresis in the N₂adsorption/desorption isotherm show that the textural pores are retainedeven after the framework pores are thermally collapsed by calcination at1000° C. (cf., FIG. 3). Thus, the textural porosity can be tailored to aparticular materials application by simply controlling the polarity ofthe solvent for supramolecular assembly.

The relationship between fundamental particle size and solvent polaritymost likely is determined by the relative rates of I° hydrolysis andsupramolecular assembly in the reaction medium. A water-rich mediumleads to rapid nucleation of the mesostructure. For assembly in 90:10(v/v) water:ethanol, a solid product is formed virtually within minutesof mixing the reagents at ambient temperature. This leads to rapidnucleation and the formation of irregularly shaped fundamentalparticles. The fundamental particles further aggregate into aself-similar, fractal-like agglomerates (cf., FIG. 4A). However, in thelower polarity 35:65 (v/v) water:ethanol solvent, I° hydrolysis andmesostructure assembly is relatively slow, requiring several hours atambient temperature for the onset of product formation. The slowernucleation and growth of the mesostructure results in spheroid to diskshaped fundamental particles 100 nm or larger in size. These fundamentalparticles interpenetrate to form even larger aggregates withinterparticle voids beyond the mesopore range (cf., FIG. 4B).

The role of mesitylene as an auxiliary structure director is highlydependent on the polarity of the medium in which mesostructure assemblyis carried out. As shown by the results in Table 1 for silicas assembledin the water-rich medium, mesitylene enlarges the framework pores andincreases the textural mesoporosity. On the other hand, for assembly inthe ethanol-rich medium, mesitylene reduces the framework pore size anddecreases still further the already low textural pore volume.

The role of mesitylene on the framework pore structure is intriguing.Mesitylene is known to bind to surfactant micelles in at least twobinding states, namely, in a “dissolved” state at the hydrophobic centerof the molecule, and in an “adsorbed” state at the hydrophilicmicelle/solvent interface (Mukerjee, P., et al., J. Phys. Chem. 82:1620(1978); Eriksson, J. E., et al., Acta Chem. Scand., 20:2019 (1966); andGordon, J. E., et al., J. Phys. Chem. 74:957(1970)). It is reasonable toexpect the equilibrium between these structurally distinct states todepend on the polarity of the solvent in which the surfactant micellesare formed. In accordance with the structurally distinct binding statesof mesitylene in surfactant micelles, the mechanism illustrated in FIG.7 is proposed for the expansion or contraction of the framework pores bymesitylene during the assembly process. In water-rich solvent, in whichthe solubility of mesitylene is low, the “dissolved” binding stateshould be favored over the adsorbed state. In this case the size of themicelle will be increased and this will be manifested as an enlargedpore in the mesostructure. But in the lower polarity ethanol-richsolvent, the solubility of mesitylene in the medium will be increasedand this will favor binding at the “adsorption” site. Hydrogen bondingbetween the π-electrons of the aromatic and water dipoles associatedwith the polar head groups at the micelle-solvent interface is believedto stabilize the adsorbed state of mesitylene (Mukerjee, P., et al., J.Phys. Chem. 82:1620 (1978)). Binding of mesitylene at the micellesurface increases the size of the effective polar head group, leading toa decrease in the radius of curvature, a reduction of micelle size, anda corresponding smaller framework pore size in the mesostructure.

In application Ser. No. 355,979, filed Dec. 14, 1994, describing theassembly of silica molecular sieves in 50:50 (v/v) water:ethanol, it wasshown that certain alkylamine surfactants (e.g., dodecylamine) gavederivatives with high textural mesoporosity whereas others affordedrelatively low textural pore volumes (e.g., tetradecylamine) (Tanev, P.T., et al., Chem. Mater 8:2068 (1996)). It is now apparent that thedegree of textural mesoporosity is quite sensitive to both the solventpolarity and the nature of the S° surfactant. The results of the presentwork show that dodecylamine and tetradecylamine afford high texturalmesoporosity when the solvent is highly polar, as in 90:10 (v/v)water:ethanol (cf., FIGS. 1 and 2).

The preferred materials in Ser. No. 355,979 were described as neutralframework analogs of hexagonal MCM-41 (Tanev, P. T., et al., Science267:865 (1995)). Evidence for the hexagonal ordering of channels wasobtained from selected area electron diffraction (Tanev, P. T., et al.,Nature 368:321 (1994)). The X-ray powder diffraction patterns were,attributed to a very small scattering domain size. It is clear from theresults of the present invention, however, that the broad diffractionlines characteristic of materials are not due exclusively to a smallscattering domain size. The patterns obtained for the fractal-like, finegrained particles are indistinguishable from those obtained for the muchlarger spheroid to disk-like fundamental particles (cf., FIG. 6).Consequently, framework disorder, in addition to small scattering domainsizes, plays an important role in broadening the diffraction lines. Onthe basis of the TEM images obtained in the present work (cf., FIGS. 4and 5), there is no evidence for hexagonal long range channel packingorder. Even “disordered” hexagonal channel packing, which has beenpreviously documented for MCM-41 prepared by S⁺I⁻ assembly (Chen, C. Y.,et al., Microporus Mater 4:1 (1995)), appears to be difficult to achieveby S°I° assembly.

Wormhole motifs have been observed for silica and alumina mesostructuresobtained by N°I° assembly, where N° is a polyoxyethylene surfactant(Bagshaw, S. A., et al., Science 269:1242 (1995); Bagshaw, S. A. et al.,Angwen. Chem. Int. Ed. Engl. 35:1102 (1996); and Prouzet, E., et al.,Angwen. Chem. Int. Ed. Engl. 36:516 (1997)). Also, sponge-like frameworkstructures have been described for mesoporous silicas obtained byelectrostatic S+I⁻ assembly in the presence of a structure disrupter(e.g., ethylenediaminetetraacetate) (Ryoo, R., et al., J. phy. Chem.100:17718 (1996)). Distinguishing between wormhole and sponge-like porestructures is not a straight forward matter. “Wormholes” imply channelstructures, whereas “sponges” imply reticulated structures. On the basisof the relatively narrow HK pore size distributions observed in thepresent work and the presence of channel-like voids in the TEM images,the preferred materials of this invention are described as wormholeshaped channels.

The solvents used in the preparation of the compositions of thisinvention are mixtures of watr and a miscible organic solvent. The wateris needed in part to cause hydrolysis of the inorganic precursor and themiscible organic solvent helps to solubilize the structure directingsurfactant. The preferred miscible organic solvents are an alkanolcontaining 1 to 10 carbon atoms. However, other polar organic moleculessuch as aldehydes hetones, esters and nitrites can be used. Inparticular, acetone, acetylacetate are suitable substitutes.

The foregoing description is only illustrative of the present inventionand the present invention is limited only by the hereinafter appendedclaims.

We claim:
 1. A quasi crystalline inorganic oxide composition havingframework-confined mesopores prepared by a method which comprisesreacting a neutral amine template and a neutral inorganic oxideprecursor wherein the template is dissolved in a solution of water and amiscible organic solvent, containing a larger volume of either themiscible organic solvent or the water, aging of the precipitate andremoval of at least some of the template and the aqueous solution toform the quasi crystalline composition which has regular wormhole shapedchannels.
 2. The composition of claim 1 wherein there is a larger volumeof water than the miscible organic solvent, and wherein the compositionhas, after calcination, a N₂ adsorption-desorption isotherm with ahysteresis loop at a partial pressure above about 0.4.
 3. Thecomposition of claim 1 wherein the composition has a specific surfacearea from about 300 to 1500 m²/g.
 4. The composition of claim 1 whichhas an X-ray diffraction pattern with at least one peak corresponding tod-spacing of at least 30 Å.
 5. The composition of claim 1 wherein themolar ratio of amine template to inorganic oxide (IO_(m)) before thetemplate has been removed, is between about 0.05 and 3 to
 1. 6. Thecomposition of claim 1 wherein the quasi crystalline inorganic oxidecomposition has the formula: A_(x)Si_(Y)O_(z) wherein A is selected fromthe group consisting of Ca, Mg, Zn, Cu, B, Al, Ga, Cr, Fe, Ge, Ti, V,Zr, V, Sn, W and Mo, x is between 0 and 1.0, y is between about 0 and1.0 and z is between about 1.0 and 3.0 and the sum of x +y is equal to1.0.
 7. The composition of claim 6 wherein A is A1, x is between 0 and0.33 and y is between 0.67 and 1.00, and z is between 1.8 and 2.0 whensum of x+y is equal to 1.0.
 8. The composition of claim 1 containing thetemplate.
 9. The composition of claim 1 with out the template which hasbeen removed by extraction with a solvent for the template.
 10. Thecomposition of claim 1 which is calcined.
 11. A composite materialprepared from the composition of claim 1 admixed with a materialselected from the group consisting of amorphous, quasi crystalline andcrystalline materials.
 12. The composition of claim 1 which is calcinedand then in addition impregnated with at least one metal compound orelement in the mesopores.
 13. The composition of claim 1 which has beencalcined and contains an organometallic compound in the mesopores. 14.The composition of claims 12 and 13 in which the metal compound,metallic element or organometallic compound is selected from the groupconsisting of Cu, Co, Cr, Ni, Fe, Ti, V, W, Mo, Pt, Pd, Ir and Sn. 15.The composition of claim 1 wherein the solution of the template containsan organic compound which is essentially insoluble in water and solublein the watr miscible organic solvent.
 16. The composition of claim 15wherein the organic compound is mesitylene.